The operations of wind farms nationwide are to be reviewed following the South Australian blackout, after a new study found technical issues shut many wind generators down.
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A second report by the Australian Energy Markets Operator into the incident was released on Wednesday and pointed to a series of voltage disturbances, which caused nine of the 13 wind farms in operation in South Australia at the time to shut down.
"Nine of the 13 wind farms online at the time of the event did not ride through the six voltage disturbances, resulting in a loss of 445MW of generation," it said in the report, which follows a preliminary report released almost a fortnight ago.
"Preliminary discussions with wind farm operators suggest this inability to ride through all disturbances was due to 'voltage ride-through' settings", which automatically disconnect or reduce output when between three to six disturbances are detected within a short timeframe, the report notes.
"The intermittent nature of wind energy had nothing to do with the September blackout," South Australian Energy Minister Tom Koutsantonis said in a statement. "This is a software issue – not a problem with renewable energy."
The energy market body said it would now "work with wind farm participants across the NEM [national electricity market] to understand the ride-through capability for each wind farm".
BHP Billiton is revising down output from its large Olympic Dam project in South Australia due to the prolonged supply disruption, pointing to the need for "secure and stable electricity supply" in South Australia and throughout the rest of Australia, it said in a production report released on Wednesday.
At the time of the statewide blackout last month in South Australia, 883 megawatts of wind power was in operation along with 330MW of gas, with a further 613MW of electricity being imported from Victoria that, in total, was supplying the 1895MW of demand in the state, the report notes.
Gas-fired power stations remained in operation until the South Australian grid disconnected from the national electricity market, it says, with the link to Victoria via the Heywood Interconnector continuing to supply power until there was a sharp rise in the flow of electricity into South Australia as generators there shut down, which subsequently caused the interconnector to automatically shut down, to protect itself.
Since the widespread blackout, some wind farm operators have changed their settings so they can continue to operate through successive voltage disturbances, the report notes. The settings had been determined by the equipment manufacturers, the report says.
The report also highlights delays in restarting the gas-fired power stations near Adelaide, although the restoration of some supplies began within three hours of the blackout "with all load that could be restored (approximately 80-90 per cent) being restored within a further five hours".
"Following the construction of temporary towers, and the restoration of three of the four damaged transmission lines, ElectraNet was able to meet all power requirements in SA from late evening on 12 October 2016," it says.
The transmission faults did not cut supply from the relevant wind farms to Adelaide, the chief executive of the Australian Energy Council, Matthew Warren, said in a statement.
"Wind farms, like other sources of generation, can be designed to ride through these types of voltage events," Mr Warren said, "there is ongoing investigation about why this occurred, which will inform how we can run a more stable and reliable system in the future."
